1. Technical Field
The present disclosure relates to power source circuits, and particularly, to a power source circuit for use in a digital subscriber line (DSL) modem.
2. Description of Related Art
DSL modems typically include a storage capacitor. The storage capacitor charges when the DSL modem is working properly and discharges to provide power for the DSL modem for a brief period in case of power failure. As such, the DSL can send a dying gasp signal to a digital subscriber line access multiplexer (DSLAM) where the DSL modem is connected for a brief period without external power. Thus, the DSLAM can release a channel assigned to the DSL modem to increase network resource efficiency.
However, the DSL modems typically work at a relatively low voltage. Therefore, to charge with sufficient charge to be a successful temporary power supply, it is required to increase a capacitance of the storage capacitor.
However, cost and size of the storage capacitor will undesirably increase with the increase of the capacitance.
Therefore, the DSL modems typically deploy a booster transformer to increase the input voltage before charging the storage capacitor. However, the booster transformer wastes power, decreasing power efficiency.
Therefore, it is desirable to provide a power source circuit for a DSL modem, which can overcome the above-mentioned limitations.